Lexus ES300 (2002 year). Manual — part 114

CHASSIS – SUSPENSION AND AXLE

CH-43

211CH43

Damping Force Characteristic

Screw Mechanism

Soft Damping
Force Valve

Base Valve

Step Meter

Spool Valve

Hard Damping
Force Valve

Damping
Force

Expansion Stroke Side

Piston Speed

Construction Stroke Side

211CH42

COMFORT

NORMAL

SEMI-
SPORT

SPORT

211CH44

Damping Force

Expansion Contraction Expansion Contraction

Expansion Contraction

Expansion Contraction

Soft

Hard

Front and Rear Shock Absorber

The basic construction and operation of the shock absorbers on the ’02 ES300 are the same as those of the

’01 ES300. However, the damping force of the shock absorbers has been changed for the ’02 ES300.

The piston rod of the shock absorber is equipped with an internal actuator. The actuator consists of a step

motor, a screw mechanism (which converts the rotational movement to a linear movement) and a spool
valve. Also, the piston rod is equipped with a soft damping force valve and a hard damping force valve.

Signals from the absorber control ECU activate the actuator causing the spool valve to switch the oil

passage. Thus, the volume of oil that passes through each valve is varied in order to control the damping
force in 16 steps.

Flow of Oil

CHASSIS – SUSPENSION AND AXLE

CH-44

7. Electronic Modulated Suspension System Control

General

The electronic modulated suspension system of ’02 ES300 and ’01 ES300 are compared below.

Control

Function

’02 ES300 ’01 ES300

Non-Linear

Smoothly changes the damping force to a target
value in accordance with the changes in the road
surface or driving conditions. Thus, excellent ride

Semi-Active
Control

Non-Linear
H

∞

Control

surface or driving conditions. Thus, excellent ride
comfort has been realized while ensuring a level
of vibration damping performance that is higher
than the sky-hook control of the ’01 ES300.

—

Control

Sky-Hook

Changes the damping force to a target value in
accordance with the changes in the road surface
or driving conditions

Thus

excellent ride

Sky-Hook
Control

or driving conditions. Thus, excellent ride
comfort has been realized while ensuring a high
level of vibration damping performance.

—

Thumping Sensitive Control

When the road surface condition does not
require a damping force, this function controls
the shock absorbers so that their damping force
will not increase.

Unsprung Vibration Control

If unsprung resonance is detected, this function
controls so that the damping force will not
decrease below a certain level, in order to
reduce the unsprung resonance.

Imaginary Roll Damper
Control

Changes the damping force to control the
vehicle posture during cornering. As a result,
excellent stability and controllability have been
realized during cornering.

—

Anti-Roll Control

During cornering, this function makes the
damping force firmer, thus restraining the body
roll speed in order to realize excellent stability
and controllability.

—

Anti-Dive Control

During braking, this function makes the
damping force firmer to restrain the body dive,
thus ensuring excellent stability and
controllability.

Anti-Squat Control

During acceleration, this function makes the
damping force firmer to minimize the changes
in the vehicle body posture.

High Speed Control

This function varies the variable range of the
damping force according to vehicle speed in
order to realize a soft and comfortable ride and
a stable driving condition.
The damping force is controlled at a softer
variable range at low speeds, and at a firmer
variable range at high speeds.

Control by Absorber
Control Switch

The absorber control switch enables the driver to
select a desired damping force from the 4 modes.

Fail-Safe

When the absorber control ECU detected a
malfunction, the control of the damping force
will be limited.

Diagnosis

When the absorber control ECU detects a
malfunction, the absorber control ECU makes a
diagnosis and memorizes the failed section.

CHASSIS – SUSPENSION AND AXLE

CH-45

211CH45

Acceleration
Sensors

Unsprung

Information

Shock

Absorber
Stoke
Information

Steering Angle Sensor

Non-Linear
H

∞

Control

Imaginary
Roll Damper
Control

Absorber
Control
ECU

Thumping
Sensitive

Unsprung
Vibration

High Speed

Anti-Squat

Anti-Dive

Control by
Absorber
Control Switch

Speed
Sensors

Engine Speed

Stop Light Switch

Absorber
Control
Switch

Shock Absorbers

Control Diagram

CHASSIS – SUSPENSION AND AXLE

CH-46

211CH46

Acceleration Sensors

Steering Angle
Sensor

Absorber Control ECU

Unsprung
Information

Non-Linear
H

∞

Control

189CH52

’02 ES300

(Non-Linear H

∞

Control)

’01 ES300

(Sky-Hook Control)

Acceleration

(m / s

2

)

Shock Absorbing State

Time (s)

Acceleration

(m / s

2

)

Shock Absorbing State

Time (s)

189CH51

Semi-Active Control (Non-Linear H

∞

Control)

To effect this control, the unsprung information is calculated based on the sprung acceleration rate from

the 3 acceleration sensors and the information from the steering angle sensor. Thus, the driving conditions
of the vehicle are detected.

This control smoothly changes the damping force to a target value in accordance with the changes in the

road surface or driving conditions. Thus, excellent ride comfort has been realized while ensuring a high
level of vibration damping performance.